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REF3333: Measuring the Output of REF3333

Part Number: REF3333

Hi TI Team,

I have a query regarding measurement of REF3333 output voltage via microcontroller ADC. For better accuracy, we plan to measure the output voltage from REF3333 in ADC. Will there be a dip in output voltage during measurement? The datasheet says the part can provide 5mA. Is there a formula/equation which shall inform about the dip in voltage during ADC measurement?

Thanks,

Rohan

  • Hi Rohan,

    If my understanding is correct, you want to make sure that the REF3333 won't dip too low in voltage during the conversion phase of the ADC's function, right?

    Do you have information on the desired sampling rate, the current draw of the ADC from its reference pin and the capacitance placed next to the uC/ADC reference pin? Using this information, we can get an idea of how much the reference voltage could be affected.

    -Tony

  • Hi Tony,

    Yes, your understanding is correct. Following is the information you need:-

    Sampling time is 2 millisec

    Capacitance is 0.1uF

    Consumption is based on ADC settings. Attaching table for your reference. Pls provide info as per table attached.

    Thanks,

    Rohan

  • Hi Rohan,

    A 12-bit ADC with a sampling period of 2ms will not have any problem recouping voltage over that period.

    Note that the highest current needed (per your table above) is 990uA which is well below the 5mA output current specified by the REF3333. This gives us plenty of margin to work with.

    If you had a 16 bit ADC and faster sampling rate, it might be worth doing a calculation, but for your situation, you should be fine. Take a look at the following article if you would to get a more in depth treatment of voltage reference considerations: www.ti.com/.../snaa320.pdf

    -Tony